The present invention generally relates to the removal of certain salts, such as those of calcium or magnesium, from water. More particularly, the present invention is directed to a method for efficiently softening water containing certain ions in a manner which limits the volume amount of undesirable waste that is sent to municipality waste treatment systems. Additionally, the present invention includes a water softening apparatus and system useable in small domestic water softeners and existing water and drainage lines.
xe2x80x9cHardxe2x80x9d water is water which contains dissolved ions, particularly calcium or magnesium ions. These ions react with soaps, which are sodium salts of stearic acid and similar organic acids, to produce a curdy precipitate of calcium and magnesium salts. When hard water occurs in residential waterlines, residents will note that the dissolved calcium or magnesium ions form a precipitant xe2x80x9cscumxe2x80x9d with soap, which may be seen in residential areas as a bathtub ring, or as a scum which adheres to clothing. In addition, hard water impedes the formation of a soap lather useful in cleansing processes. Hard water can present a considerable problem in washing, reducing the efficiency of boilers, heating systems, and other apparatus, and in certain industrial process use. Accordingly, it is often desirable to provide a means for removing the unwanted calcium or magnesium salts from the hard water, thereby to provide xe2x80x9csoftxe2x80x9d water which does not contain such ions. This process is known as xe2x80x9csofteningxe2x80x9d water.
The main cause of hard water is generally dissolved calcium bicarbonate (Ca(HCO3)2). In limestone or chalk regions, calcium hydrogencarbonate is formed by the action of dissolved carbon dioxide on calcium carbonate. In some areas, hardness also results from dissolved calcium sulfate (CaSO4).
A common method of softening water, such as in small domestic water softeners, involves the process of ion exchange. Ion exchange is a process whereby a water solution is passed through a column of a material that replaces one kind of ion in solution with another kind. Such materials are known as ion exchange resins. Home and commercial water softeners generally contain cation-exchange resins. These resins consist of insoluble macromolecular substances to which negatively charged groups are chemically bonded. The negative charges are counterbalanced by ions such as sodium ions. When hard water containing the calcium or magnesium ion passes through a column of this resin, the sodium ions in the resin are replaced by calcium or magnesium ions. The reaction may be generalized as follows for calcium:
2NaR(s)+Ca2+(aq)xe2x86x92CaR2(s)+2Na+(aq)
where Rxe2x88x92 is an anion of the exchange resin. The reaction for magnesium (Mg2+) is similar to the reaction for calcium.
Water that has passed through the column containing the ion exchange resin contains sodium ions in place of calcium or magnesium ions, and has been softened. Once the resin has been completely converted to a calcium and/or magnesium salt, it can be regenerated by flushing the column with a concentrated solution of sodium chloride to reverse the previous reaction.
To perform this process in residential and industrial use, water softeners generally consist of a resin vessel filled with softening resin, a riser tube that has a screened opening at the bottom of the resin vessel and that extends through a vessel inlet/valve outlet in the resin vessel, and a multi-port valve that directs the flow of water through different channels to and from the resin vessel. In the service cycle, when water is being softened, the hard water would flow through the multi-port valve and into the resin vessel from the outer diameter of the vessel inlet/valve outlet. The water would then go through the resin bed and become softened. The softened water then flows through the screened opening in the riser tube at the bottom of the resin vessel, through the multi-port valve and to the home water supply.
Once the resin has been completely converted to the calcium or magnesium salt, the resin must be regenerated. During regeneration, most softeners flow brine (which is formed by dissolving common rock salt in water) in the same direction as the service flow, and direct the water from the riser tube through the multi-port valve to a common drain, which is generally connected to a sewer. Some softeners may use a countercurrent flow of brine, but also direct all waste to the drain.
The regeneration process generally includes several steps, including a backwash, brine injection, a slow rinse and a fast rinse. While there may be some slight variations in different water softeners (for example, the sequence of the steps or the direction of flow may be different for some configurations), most water softeners generally utilize the same regeneration principles.
For example, in the backwash step water is directed down through the riser tube and flows upward in the resin vessel. This step lifts the resin bed and directs the waste through the outer diameter opening of the resin vessel, through the multi-port valve and to the drain.
The step of brine injection generally involves opening an inlet valve to an eductor/injector. The eductor/injector is generally a venturi valve. The inlet valve is connected to a brine tank, such as with a flexible tube. Brine in the brine tank is formed by water and rock salt that a user puts in the brine tank periodically. Water is generally provided by a step in the regeneration process which directs water through the multi-port valve to the brine tank. The brine tank generally does not require any agitation, rather it simply saturates by soaking in the salt. The brine injection step includes sending city water at full pressure past the venturi valve, thereby causing a pressure gradient and sucking brine in from the injector to mix with the city water (or water from other water sources, such as well water) used to cause the pressure drop. This mixture is directed through the resin bed, up the riser tube, and out the common drain. The cycle is timed to allow the resin exposure to a specific mass of sodium chloride, which is directly proportional to the capacity desired. Generally, the maximum salt required for achieving maximum resin regeneration capacity is exposed to the resin. After a specific amount of time has elapsed, therefore, the brine inlet valve is closed.
During the slow rinse step, city water (or water from a given water source) continues to be sent through the venturi valve. The venturi valve now acts as a flow control device and sends a slow stream of water to the resin bed, thereby rinsing the salt out. The waste is directed to the city drain. During the fast rinse step, city water is allowed to flow at full flow through the resin bed and the water is then directed to the city drain. This step packs the resin bed as well as purges any remaining salt out of the resin vessel. During this cycle, most water softeners also open the brine valve and refill the brine tank. A miniature float check valve in the brine tank shuts off flow when the brine tank has reached its capacity.
The multi-port valves for use with such water softeners consist of various types. For example, Autotrol, a division of Osmonics, located in Minnetonka, Minn., uses flapper valves; Fleck Valves, located in Brookfield, Wis., uses a moving piston with openings at different points, and Erie Valves, located in Milwaukee, Wis., uses a revolving disk with openings at different points.
Because self regenerating water softeners send the waste down the home drain to municipality waste treatment systems, excessive salt levels in the water prevent municipalities from reclaiming the waste water for irrigation and other use. There is increasing pressure from these municipalities, accordingly, to ban self regenerating water softeners. For example, some major areas where water is becoming scarce already do not allow these devices. For example, Irvine, San Diego, San Bernardino and Riverside Counties in California do not allow the use of self regenerating home water softeners. Further, as of 1999 there are bills in the California Assembly to ban such devices altogether in California. In other parts of the country where water is scarce, the use of such self regenerating home water softeners may be additionally at risk.
Accordingly, the water softener industry has been aggressively attempting to improve the efficiency of the devices they manufacturer. Devices currently on the market, however, do not reduce the volume of regeneration water enough to economically eliminate discharge to the sewer. Accordingly, it can be seen that there is a need for a new method for softening water with ion exchange which achieves a drastic reduction in waste volume. Further, it can be seen that there remains a need for a new water softener that reduces the waste volume sent to municipality waste treatment systems, and which allows the salt waste to be economically disposed of through alternative disposal routes. The present invention is directed to meeting these needs.
It is an object of the present invention to provide a new and useful method for reducing the waste volume in domestic and industrial water softeners.
It is another object of the present invention to economically minimize or eliminate discharge of water softener regeneration waste to the sewer.
It is yet another object of the present invention to provide a low cost means for softening water which limits or eliminates the levels of salts sent to municipality waste treatment systems.
A still further object of the present invention is to provide a water softening apparatus which is efficient and economical and which minimizes waste discharge to the city sewer line.
Yet another object of the present invention is to provide a system for softening water which works with the present city water and drainage lines.
Accordingly, the present invention provides a water softening apparatus that is adapted to be placed in fluid communication with a water drain, a processing device, a water source that provides water containing undesired ions, and a water tap that dispenses water for consumption, wherein the water softening apparatus is operative to remove the undesired ions from water processed thereby. The water softening apparatus comprises a resin vessel containing an ion-exchange resin that is capable of chemically shifting between an active state and an exhausted state, a regenerant reservoir adapted to receive a regenerant solution containing selected preferred ions, and a manifold in fluid communication with the resin vessel and the regenerant reservoir.
The manifold has a first inlet in fluid communication with the water source, a first outlet in fluid communication with the water tap, a second outlet in fluid communication with the water drain, and a third outlet in fluid communication with the processing device. The manifold includes a plurality of fluid pathways communicating between the inlet, the outlets, the resin vessel and the regenerant reservoir. A plurality of valves associated with the fluid pathways are configurable into a plurality of valve states. In a first valve state, fluid circulates through the first inlet, through the resin vessel and through the first outlet. In a second valve state, fluid circulates from the regenerant reservoir through the resin vessel and through the second outlet. In a third valve state, fluid circulates from the regenerant reservoir through the resin vessel and through the third outlet. In a fourth valve state, fluid circulates through the first inlet, through the resin vessel and into the regenerant reservoir. In an optional fifth valve state, fluid circulates through the first inlet, through the resin vessel and through the second outlet.
The water softening apparatus may include a pump and a flow controller in fluid communication with the regenerant reservoir and the manifold. The resin vessel may include a first combination inlet/outlet in fluid communication with the first inlet of the manifold and a second combination inlet/outlet in fluid communication with the first outlet of the manifold. The first combination inlet/outlet may also be in fluid communication with the third outlet of the manifold, and the second combination inlet/outlet may also be in fluid communication with the regenerant reservoir. The resin vessel may further include a resin vessel outlet in fluid communication with the second outlet of the manifold. The manifold itself may additionally include a third combination inlet/outlet in fluid communication with the regenerant reservoir.
The manifold is preferably a modified Autotrol Series 169 multi-port valve. The ion-exchange resin may be a shallow shell/shortened diffusion path resin or small bead size resin, and is preferably a Purolite SST or Purolite C100FM resin.
The present invention is also directed to a water softening system that comprises a water softening apparatus according to the present invention, a water source that provides water containing undesired ions such as calcium and magnesium ions, a water tap that dispenses water for consumption, a water drain, and a processing device such as an evaporation device.
The present invention is further directed to a method for softening water that contains undesired ions. The method comprises providing an ion-exchange resin, contacting the ion-exchange resin with the water that contains the undesired ions when the ion-exchange resin is shifted toward its active state, contacting the ion-exchange resin with a regenerant solution containing the selected preferred ions when the ion-exchange resin is shifted toward its exhausted state so as to form a waste solution containing the undesired ions, and collecting the waste solution thereby to permit selective disposal of the undesired ions via a processing device that is separate from a drainage line.
The ion-exchange resin may be provided in a resin vessel that is sized and adapted to receive a selected volume of a fluid. The step of contacting the ion-exchange resin with the regenerant solution may include first contacting the ion-exchange resin with the selected volume of the regenerant solution thereby to displace the selected volume of water from the resin vessel, and passing the selected volume of water to a water drain. The step of contacting the ion-exchange resin with the regenerant solution may include transporting, such as by pumping, the regenerant solution from a regenerant reservoir into the resin vessel, and may include contacting the ion-exchange resin with between 0.25 and 2.0 bed volumes of the regenerant solution. The step of collecting the waste solution may include transporting the waste solution to an evaporation device.
The method may further include the step of rinsing the ion-exchange resin with water thereby to form a rinse solution and thereafter transporting the rinse solution to the regenerant reservoir, and the step of adding rock salt to the regenerant reservoir, thereby to form a brine solution from the rinse solution.
These and other objects of the present invention will become more readily appreciated and understood from a consideration of the following detailed description of the exemplary embodiment of the present invention when taken together with the accompanying drawings, in which: